Don't do as I did by removing this
Diopter Adjusting Knob. The camera
can be removed from the rear case
by lifting up on the opposite end
and rocking it out. This is a bear to
reassemble. The little spring fits
down into a hole, the ball is placed
on the end of the spring, then the Knob
is placed over and retained with the screw.
That little ball has a mind of its own.
Jumps off the spring and hides. The last time
it hid for good and I never did find it.
So as a replacement, in my junk drawer was
a tiny ball bearing from my model building
days. I took it apart and found the balls
were the same size.